Boosting device, such as turbochargers and superchargers, may be used in engines. Turbochargers may increase the power output of the engine for a given displacement as compared to a naturally aspirated engine.
It may be desirable to decrease the flow path between the turbine in the turbocharger and the combustion chambers by positioning the turbine close to the exhaust ports of the cylinders. Such positioning decreases losses in the exhaust gas flow, thereby enabling the speed of the turbine to increase. The increased turbine speed increases the amount of compression provided by the compressor. As a result, the power output of the engine may be increased.
However, due to the proximity of the turbine to the combustion chamber, the turbine and surrounding components may experience elevated temperatures. In some engines the exhaust manifold and turbine housing may have radiating surface temperatures over 900 degrees Celsius. Consequently, the turbine and surrounding components may experience thermal degradation, decreasing component longevity. For example, wastegates may become inoperable during such over-temperature conditions. Wastegate actuators may be particularly susceptible to elevated temperatures due to the characteristics of the valve control component included therein, such as circuits, solenoids, etc.
U.S. Pat. No. 4,630,445 discloses a turbocharger with a wastegate valve for adjusting the amount of exhaust gas provided to a turbine in the turbocharger. A heat shield is used in the wastegate to protect the valve stem in the wastegate from elevated temperature conditions. The Inventors have recognized several drawbacks with the wastegate valve disclosed in U.S. Pat. No. 4,630,445. For example, the heat shield may reduce the amount of heat transferred to the wastegate but does not actively cool the wastegate. Furthermore, heat may be transferred to the wastegate components from paths which are not impeded by the heat shield. Consequently, the wastegate valve disclosed in U.S. Pat. No. 4,630,445 may still experience over-temperature conditions during engine operation.
Likewise, attempts have been made to cool the wastegate actuator via engine coolant diverted from the engine cooling system. However, utilizing engine coolant to cool the wastegate actuator may require high integrity plumbing and increases the likelihood of coolant leaks through new leak paths. The high integrity plumbing may also be costly.
As such in one approach a turbocharger system is provided. The turbocharger system includes a turbine positioned downstream of a combustion chamber, a turbine bypass conduit in fluidic communication with a turbine inlet and a turbine outlet, a wastegate positioned in the turbine bypass conduit, and an air-cooled wastegate actuator adjusting the position of the wastegate, the air-cooled wastegate actuator receiving cooling airflow from an intake conduit positioned upstream of a compressor mechanically coupled to the turbine.
In this way, cooling is provided to the wastegate actuator via intake air, thereby reducing the thermal stress on the actuator. Consequently, the longevity of the wastegate actuator may be increased when air cooling is provided. Furthermore, when intake air is used to cool the wastegate actuator, cooling of the wastegate actuator via engine coolant may be avoided or reduced, if desired. As a result, the cost and complexity of the engine is reduced and the likelihood of coolant leaks and potential cooling system degradation is reduced.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.